Directional well drilling practices are well known in the well drilling art. Directional drilling is often necessary to prevent unwanted well bore deviation and often economically advantageous in producing well bores that reach laterally from the drilling site to the production zone.
Devices used just above the drill head to cause lateral deflection of the well bore being drilled have progressed from primitive to complex in the years of expansion of the use of downhole motors and Measurement While Drilling (MWD) instrumentation. Such evolution has been a slow process, each step of which is well known to those skilled in the well drilling art.
Conventional drilling practices require tripping the drill string to change the drill head. For many years a common drill head might last no more than thirty hours. The frequent inevitable tripping of the drill string made servicing the downhole assembly used for directional control a minor burden. Drill heads, both diamond and roller, may now last over two hundred hours. Special drill string trips to change directional control apparatus is now parasitic to the system. There is an understandable urge to develop downhole apparatus that will allow change of downhole apparatus between straight and directional drilling configuration without tripping the drill string.
Changing the configuration of the downhole drilling assembly has been made possible without tripping the drill string by the use of wire line tools run down the drill string bore. This too takes time and causes some problems, some of which are dangerous. It is very desirable to do the same thing by manipulation of drilling fluid flow controls that are always present. Downlink command of configuration change by way of flow controls places no additional technical burden on surface gear and little additional technical burden on operating personnel.
It is therefore an object of this invention to provide a downhole drill string deflecting apparatus to change between straight drilling and directional drilling configuration in response to preselected manipulations of drilling fluid flow controls at the surface.
It is a further object of this invention to provide a remote control selector valve that is responsive to preselected drilling fluid flow manipulations to direct the action of the downhole deflecting machinery so that the change between the two configurations may be repeatedly exercised.
It is yet another object of this invention to provide apparatus that will produce a drilling fluid pressure drop in the apparatus that is representative of the configuration of the apparatus downhole.